In a survey of nematodes associated with potato conducted in six major potato-producing regions of Saudi Arabia from 1989 to 1991, following genera in descending order of frequency were found : Aphelenchus (40%), Ditylenchus (28%), Tylenchorhynchus (20%), Meloidogyne (19 %), Aphelenchoides (10%), Tylenchus s.I.(9%), Subanguina ( 6% ), Trichodorus (5%), Pratylenchus and Helicotylenchus (2%), Macroposthonia (0.7%) and Paratylenchus and Cacopaurus (0.2%). Distribution frequency and population density of these genera varied among the six regions - Hail and Tabuk were the lowest with respect to diversity and density, Gassim and Riyadh were moderate and Hofuf and Najran were the highest. Prominence values of the associated nematodes indicated that Meloidogyne spp. Mainly ( M . javanica ) were, by far the most prominent plant-parasitic nematodes in Saudi potato fields, followed by Tylenchorhynchus spp., and then by Ditylenchus spp. ( mainly D. destructor ).